5 ms·

Is it possible it's not the current that causes this but the leeching of ions into the soil from the electrodes?

zwieback 3y ago
I was wondering about that too but they did show a difference between the different circuit types presumably with the same electrodes.
- zdragnar 3y ago
  The open circuit and control having a similar effect show that it likely isn't ions from the anode or cathode. The other two are more interesting- presuming the short circuit had a lower effect than the one with some resistive load (labelled closed circuit), I presume there's something changing in the soil chemistry itself once sufficient potential is reached by microbe activity. Ions being knocked loose from the dirt itself, rather than the anode or cathode, which wouldn't happen when there's a direct short / no load other than the wire.
  - amluto 3y ago
    I don’t have access to the full paper, but this doesn’t follow: > The open circuit and control having a similar effect show that it likely isn't ions from the anode or cathode. When you apply current between two electrodes in an electrolyte, you do a few things: 1. Create an electric field between them. 2. Create an ionic current through bulk electrolyte. 3. Cause chemical reactions at the surfaces. This has to happen: the current in the electrode is made up of electrons (or, equivalently, holes), but the electrolyte doesn’t conduct electrons — it conducts ions. [0]. So, for charge balance to be maintained, every electron that exits the anode into the medium needs to somehow turn into an ion, which happens by chemically adding an electron to something, thus reducing it. Similarly, the cathode pulls electrons from the electrolyte, and they come from something in the electrolyte, which is oxidized as it loses the electrons. If the cathode in particular is not inert at the voltage used, the cathode itself can be oxidized. A copper cathode can, for example, produce copper ions much faster than it it would naturally leach them without an applied voltage. [0] I’m sure that exceptions exist. Solvated electrons are a thing. And you could use an electrically conductive substance as your medium, e.g. carbon or metal powder.
    - smaddox 3y ago
      Yeah, seems like they would need to use gold or platinum electrodes to rule out copper (or whatever) leaching. But even if it's copper leaching that boosts growth, that seems interesting in and of itself---just not really due to electric current.
    - tagawa 3y ago
      But according to the article, the researchers did not apply any current.
      - zwieback 3y ago
        Right, the soil makes a battery.
superkuh 3y ago
I'd really like to know if they did a control where they heated the soil around the roots with the same amount of power using a heating mat or something. My bet is that it's the heating that is inducing the changes. I wondered about electrode material too. But both questions remain unanswered because sci-hub hasn't added new articles since the 2020 attack in on them in Indian courts. I have no way to access the full text to make an informed comment. The only detail in the snippets and abstract was that it was 50mA of current. That'd be about a watt of heating for typical hundreds of ohms volume resistances of damp soil.
djmips 3y ago
But the current's got what plants crave. It's got electricity.
- ta23143254536 3y ago
  You just made my day

I was wondering about that too but they did show a difference between the different circuit types presumably with the same electrodes.

zdragnar 3y ago
The open circuit and control having a similar effect show that it likely isn't ions from the anode or cathode. The other two are more interesting- presuming the short circuit had a lower effect than the one with some resistive load (labelled closed circuit), I presume there's something changing in the soil chemistry itself once sufficient potential is reached by microbe activity. Ions being knocked loose from the dirt itself, rather than the anode or cathode, which wouldn't happen when there's a direct short / no load other than the wire.
- amluto 3y ago
  I don’t have access to the full paper, but this doesn’t follow: > The open circuit and control having a similar effect show that it likely isn't ions from the anode or cathode. When you apply current between two electrodes in an electrolyte, you do a few things: 1. Create an electric field between them. 2. Create an ionic current through bulk electrolyte. 3. Cause chemical reactions at the surfaces. This has to happen: the current in the electrode is made up of electrons (or, equivalently, holes), but the electrolyte doesn’t conduct electrons — it conducts ions. [0]. So, for charge balance to be maintained, every electron that exits the anode into the medium needs to somehow turn into an ion, which happens by chemically adding an electron to something, thus reducing it. Similarly, the cathode pulls electrons from the electrolyte, and they come from something in the electrolyte, which is oxidized as it loses the electrons. If the cathode in particular is not inert at the voltage used, the cathode itself can be oxidized. A copper cathode can, for example, produce copper ions much faster than it it would naturally leach them without an applied voltage. [0] I’m sure that exceptions exist. Solvated electrons are a thing. And you could use an electrically conductive substance as your medium, e.g. carbon or metal powder.
  - smaddox 3y ago
    Yeah, seems like they would need to use gold or platinum electrodes to rule out copper (or whatever) leaching. But even if it's copper leaching that boosts growth, that seems interesting in and of itself---just not really due to electric current.
  - tagawa 3y ago
    But according to the article, the researchers did not apply any current.
    - zwieback 3y ago
      Right, the soil makes a battery.

superkuh 3y ago

I'd really like to know if they did a control where they heated the soil around the roots with the same amount of power using a heating mat or something. My bet is that it's the heating that is inducing the changes. I wondered about electrode material too. But both questions remain unanswered because sci-hub hasn't added new articles since the 2020 attack in on them in Indian courts. I have no way to access the full text to make an informed comment. The only detail in the snippets and abstract was that it was 50mA of current. That'd be about a watt of heating for typical hundreds of ohms volume resistances of damp soil.

djmips 3y ago

But the current's got what plants crave. It's got electricity.

ta23143254536 3y ago
You just made my day